Quote:
Originally Posted by katy
STP is not an oil, it's an additive.
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Yes; the closest modern gear oil found, based on inspection of an original "600W" can is 250W, such as Penrite's or Lubriplate SPO 299. These are OK for yellow metals without additives. The ZDDP additive is usually added to engine oils to increase zinc levels but could damage catalytic convertors. That's our understanding why STP discontinued the zinc- rich red bottle in the US some years ago.